1. Field of the Invention
This invention relates to optics and more particularly to recording transmission and fluorescent emission spectra from a sample material.
2. Description of the Prior Art
It is well known that when white light is transmitted to a substance, the substance makes a frequency selective absorption of a portion of the light, the remainder being transmitted through the substance. Additionally, monochromatic light being transmitted to the substance may cause a fluorescent emission therefrom.
The phenomena of either absorption of fluorescence is often combined with a chromatographic separation technique, known as high pressure liquid chromatography, to identify substances in a mixture. Chromotographic separation was introduced by Mikhael Tswett in 1906.
In identifying the source of an oil spill, for example, a decisive factor may be a determination of light transmission characteristics of a sample of the spill. To find the light transmission characteristics, components of the sample are chromatographically separated by forcing the sample, usually under pressure, through an adsorption column. The column may be comprised of silica gel particles or any other suitable substance.
Each component passes through the column at a unique velocity. Therefore, the components pass a known location in the column with a temporal separation therebetween. An exit line from the column typically feeds a cell of a light transmission measuring instrument, such as a filter colorimeter.
Light of a selected wavelength, in the ultra-violet or visible region, is transmitted through the cell. The intensity of the light transmitted through the cell is measured by a detector, which is coupled to a recorder. Since the components have the temporal separation, recorded minima of the light transmitted through the cell is in response to transmission of light through respective ones of the components. In a similar manner, fluorescent emission from the components may be recorded.
It should be understood that the components absorb light differently from each other. Moreover, some of the components may not absorb light at the selected wavelength. Therefore, the use of the filter colorimeter has substantial limitations as an analytic tool. It is desireable to have an instrument that provides a complete spectrum of light transmitted through a component in response to white light being transmitted thereto.